This invention relates in general to reinforced thermoplastic materials and, more specifically, to such materials in which the reinforcement is in the form of rigid rod-like polymer molecules.
High strength structural materials composed of high strength fibers such as glass, graphite or aramid fibers, embedded in a flexible matrix material, such as thermoplastic resins, have long been used. While these materials have excellent properties for many applications, they are often not suitable for thin film applications. Where the fibers are in the form of fiber fabrics or mats generally, significant reshaping of the composites is difficult. Also, manufacture of complex structures by methods such as injection molding is difficult even when the reinforcements are in the form of finely chopped fibers distributed through the matrix. These fiber reinforced materials also encounter problems with interfacial adhesion and differential thermal expansion when used for some purposes.
Recently, molecular composites in which rigid, rod-like polymers are mixed with a flexible, coil-like polymer to produce a higher strength reinforced products have been developed. Typical of these are the material disclosed by Helminiak, et al, in U.S. Pat. No. 4,207,407. While these materials show promise for use in high strength films, a number of problems remain. Obtaining uniform dispersion of the rod-like molecules has proven difficult. Phase separation and agglomeration problems during processing persist. Post processing of film materials and the production of complex shapes by techniques such as press forming and injection molding have not proven practical. Thus, there remains a continuing need for improved methods of synthesizing and processing these materials in order to achieve the properties needed for structural applications.